Intellectual Disability Disorder versus Autism Spectrum Disorder: A Fragile X Syndrome Case Report
Maria João Palha1
, Francisca Palha1, İnês Munhá1,2, Sara Torres Oliveira1, Felipe Bezerra1, Miguel Palha2
1Santa Maria University Hospital – Lisbon Academic Medical Center, Neurodevelopmental and Behavioral Unit, Department of Pediatrics, Lisbon, Portugal
2Neurodevelopmental Center Diferenças, Lisbon, Portugal
Keywords: Fragile X Syndrome, Intellectual Disability, Autistic Disorder, Psychomotor Agitation
Abstract
Intellectual development disorder is a neurodevelopmental condition characterized by significant impairments in intellectual functioning and in adaptive behavior, with onset during the developmental period. It is often accompanied by neurodevelopmental and behavioral comorbidities such as autism spectrum disorder, attention deficit hyperactivity disorder, and other behavioral disturbances not specified. Fragile X syndrome is the most common inherited cause of intellectual disability disorder and frequently presents with overlapping neuropsychiatric and behavioral features, complicating diagnosis and management.
This report presents the case of a six-year-old boy previously diagnosed with autism, who was evaluated due to restlessness, irritability, and aggressiveness beginning at 12 months of age. He exhibited deficits in intellectual functioning and adaptive behavior. He was subsequently diagnosed with comorbid intellectual disability, autism spectrum disorder, attention deficit and hyperactivity disorder, and irritability. His physical phenotype was unremarkable. Genetic testing confirmed the diagnosis of Fragile X syndrome. Treatment with risperidone and methylphenidate led to behavioral improvement.
Through this article, the authors aimed to review key aspects of the clinical assessment and therapeutic approach to intellectual disability, autism and Fragile X syndrome, contextualized within the discussion of a case report.
Cite this article as: Palha MJ, Palha F, Munhá I, Torres Oliveira S, Bezerra F, Palha M. Intellectual disability disorder versus autism spectrum disorder: a Fragile X syndrome case report. Pediatr Acad Case Rep. 2026;5(2):41-5.